The present invention relates to a concatenated sensor system comprised of a plurality of concatenated sensor units, and more particularly, to a relay device for electrically connecting adjacent ones of a plurality of sensor unit groups arranged to be spaced in a concatenated sensor system or a master unit and a sensor unit group adjacent thereto.
For control of operations of various manufacturing apparatuses, detection information detected by a plurality of sensor units of a sensor system are used in some cases. For instance, each sensor unit is composed of a sensor unit body and a detecting element connected thereto. The detecting element is located to face an object of detection in a manufacturing apparatus. The detection information detected by the detecting element is delivered to a controller of the sensor system through the sensor unit body.
In order to reduce the arrangement space of the sensor system of this type and shorten signal cables (signal conductors) used for transfer of signals between the detecting elements and the sensor unit bodies and between the sensor unit bodies and the controller, a concatenated sensor system may be used. The concatenated sensor system has sensor unit bodies thereof provided with male and female input-output connectors and is so arranged that the respective input-output connectors of the adjacent sensor unit bodies are connected to one another when the sensor unit bodies are disposed on a base in intimate contact with one another.
In the concatenated sensor system, a master unit may be provided between the controller of the sensor system and the sensor unit groups. The master unit has a setting section for collectively settings detection threshold values for the detecting elements and a display section for collectively displaying operating states of the individual sensor units.
As described above, the concatenated sensor system has such an advantage that a large number of sensor units can be arranged in intimate contact with one another, thereby reducing the arrangement space. However, depending on an object to which the system is applied, a detection signal transmission line extending from the detecting element to the sensor unit body may be lengthened, so that the detecting performance can be lowered.
In the case where the concatenated sensor system is used to detect the presence of a workpiece on the side upstream of a coating machine and check the workpiece for coating on the side downstream of the coating machine, for example, a detecting element for workpiece detection and a detecting element for coating detection are spaced from each other. Irrespective of the location of the concatenated sensor system relative to the coating machine, therefore, the distance from the sensor system to the detecting element for workpiece detection or to the detecting element for coating detection becomes long to the extent that a long signal cable (signal conductor) must be used to connect the detecting element and the sensor unit body.
In this case, laying the signal cable is laborious, and the detection information may possibly be attenuated during the transfer through the signal cable, to lower the detecting performance. When an optical fiber (optical fiber cable) is used for the signal transmission, the optical fiber cannot be laid with ease since it is more susceptible to bending than an electric cable is. If the optical fiber has a lot of bent portions, the detecting performance of the sensor units may be lowered.
This awkward situation may possibly be removed by dividing the sensor units of the concatenated sensor system into a plurality of sensor unit groups and locating the individual sensor unit groups in the vicinity of the detection objects. According to the sensor system of this type, the distance between the sensor unit body and the detecting element in each sensor unit group is short, so that the signal cable can be shortened, and lowering of the detecting performance that is attributable to the attenuation of the detection information can be avoided.
On the other hand, signal transmission is required between the sensor unit groups. In brief, two sensor units that are situated individually at the opposed ends of each two adjacent sensor unit groups can be connected to each other by means of a relay cable provided with connectors. That is, the two sensor units can be connected to each other by plugging the connectors at the opposite ends of the relay cable into connectors on the two sensor units, whereby the adjacent sensor unit groups can be connected.
However, the connection between the relay cable and the sensor units, established by means of the connectors, is not strong enough, and therefore, if a tensile force acts on the relay cable, the connectors of the relay cable may possibly be disengaged from the connectors of the sensor units. If lock mechanisms are provided on the connectors of the sensor units to prevent the disengagement of the connectors, the sensor units become complicated in construction and entail higher cost. The lock mechanism on one of each two adjacent sensor unit groups projects toward the lock mechanism on the other sensor unit group, and therefore, if the adjacent sensor unit groups are expected to be located close to each other, such close location cannot be realized. Although the connectors of the relay cable can be fastened to the sensor units with use of screws so that they are prevented from disengagement, the sensor units require a space for female screw formation, so that the sensor units are large-sized and cost high.
An object of the present invention is to provide a relay device that can securely electrically connect adjacent ones of a plurality of sensor units or sensor unit groups arranged to be spaced in a concatenated sensor system or connect a master unit and a sensor unit or sensor unit group disposed adjacent thereto.
In order to achieve the above object, according to the present invention there is provided a relay device for a concatenated sensor system including a first unit group comprised of at least one sensor unit or a master unit and a second unit group comprised of at least one sensor unit.
The relay device for the concatenated sensor system of the present invention comprises a first relay unit adapted to be juxtaposed in intimate contact with one side of the first unit group and adapted to be fixed, together with the first unit group, to a first base, the first relay unit including a first linking connector electrically connectable with a first input-output connector provided on the one side of the first unit group; a second relay unit adapted to be juxtaposed in intimate contact with another side of the second unit group and adapted to be fixed, together with the second unit group, to a second base, the second relay unit including a second linking connector electrically connectable with a second input-output connector on another side of the second unit group; and a relay cable electrically connecting the first relay unit and the second relay unit.
According to the relay device of the present invention, when the first and second relay units are juxtaposed in intimate contact with the first and second unit groups, the linking connectors of the first and second relay units are connected to the input-output connectors of the first and second unit groups, respectively. Electrical connection between the first and second unit groups can be established by connecting the first and second relay units through the relay cable.
Thus, the relay device of the present invention is used to connect a plurality of unit groups of the concatenated sensor system. By means of the relay device, a plurality of sensor units, a plurality of sensor unit groups, or the master unit and the sensor unit or the sensor unit group, for instance, can be connected to one another.
More specifically, if each of the first and second unit groups is formed of a sensor unit group, the linking connectors of the first and second relay units are connected individually to the input-output connectors on the sensor units that are situated individually at the opposed ends of the two sensor unit groups, and the two sensor unit groups are connected to each other by means of the relay cable. If each of the first and second unit groups is formed of one sensor unit, the two sensor units are connected by means of the relay cable. If the first unit group is formed of the master unit and if the second unit group is formed of the sensor unit or sensor unit group, the master unit and the sensor unit or the sensor unit group are connected by means of the relay cable.
In the case where the unit groups of the concatenated sensor system are spaced from one another, therefore, the adjacent unit groups can be connected by means of the relay device, so that each sensor unit can be located near a detection object to reduce the length of a signal conductor extending from the sensor unit to the detecting element. Thus, the signal conductor can be laid with ease, and the detecting performance of the sensor system can be ensured. Moreover, according to the present invention where the relay cable is arranged to be connected to the first and second relay units, the sensor unit or master unit need not be provided with any connecting means, such as a connector, adapted to be connected with the relay cable. This makes it possible to avoid complication of the configuration and increase in cost, which are attributable to the formation of the connecting means to the sensor unit or the master unit. According to the present invention, moreover, the first relay unit is fixed together with the first unit group to the first base, while the second relay unit is fixed together with the second unit group to the second base, which is identical with or separate from the first base, so that stability in use is satisfactory.
Preferably, in the present invention, the relay cable is connected to the first and second relay units at those outer surfaces of the first and second relay units which extend in the direction of arrangement of the first and second unit groups. With this preferred arrangement, the opposite surfaces of the first and second unit groups need not be provided with any connecting means that is adapted to be connected with the relay cable, thereby preventing increase in the dimensions, caused by the provision of the connecting means, of each of the first and second unit groups as viewed in the direction of arrangement of these unit groups. Thus, the first and second unit groups can be located close to each other as required.
In this preferred arrangement, the relay cable may have opposite ends thereof provided with connectors that are adapted to be connected individually to relay connectors provided on the outer surfaces of the first and second relay units. In this case, the electrical connection between the relay cable and the first and second relay units can be easily established by means of the connectors, and the connectors of the relay cable cannot be easily disengaged from the relay connectors even if a tensile force acts on the relay cable, since these connectors are provided on the outer surfaces.
In the present invention, preferably, end plates are arranged in intimate contact with that side of the first relay unit which is remote from the first unit group and that side of the second relay unit which is remote from the second unit group, the end plates being fixed to the first and second bases, individually. In this case, the first relay unit and the first unit group (sensor unit, sensor unit group, or master unit), as well as the second relay unit and the second unit group, can be kept in intimate contact with each other.
In the case where at least one of the first and second unit groups is a sensor unit group composed of a plurality of sensor units, the end plates are each arranged in intimate contact with that side of the sensor unit group which is remote from the relay unit and each fixed to the corresponding one of the first and second bases. In this case, the sensor unit group and the relay unit can be securely fixed between a pair of end plates.
Preferably, the concatenated sensor system of the present invention comprises a signal conductor extending from each of the sensor units to a detecting element thereof, the signal conductor being formed of an optical fiber. In the present invention, the signal conductor of each sensor unit can be shortened, so that bent portions of the signal conductor can be reduced in number. Even in the case where the signal conductor is formed of the optical fiber, therefore, deterioration of the signal transmission characteristic caused by bending of the optical fiber can be suppressed, and a detection signal from the detecting element can be satisfactorily transmitted to the sensor unit.
Preferably, in the present invention, at least one of the relay units includes a communication driver between the linking connector and the relay cable. The communication driver increases a signal transmission ability of the relay unit and allows elongation of the relay cable.
Further, the relay unit provided with the communication driver may include power supply means through which external power is supplied to the communication driver. In this case, the signal transmission ability of the communication driver can be further increased.